Thorium

Thorium is a dark grey, radioactive metal of which the principal source is the ore, monazite, a complex phosphate of thorium, uranium, cerium and lanthanides. The metal is soft and ductile and is extracted by precipitation as the hydroxide, along with cerium and uranium; separation is achieved by further extraction with tributyl phosphate from an acid solution. The metal is made by calcium reduction of the oxide or fluoride, and pure thorium can be obtained by decomposing ThI₄ on a hot filament (the Van Arkel process). Thorium is used as an alternative reactor fuel to uranium, thorium being converted readily into uranium in the reactor. Thorium is extremely efficient as an energy source, the earthly reserves of thorium containing more energy than all other fossil fuel sources combined.

Symbol

Th

Discovered

1829 by J.J. Berzelius in Stockholm.

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Atomic number	90		Clip
Atomic / Molecular Weight	232.038	gmol-1	Clip
Density	11725	kgm-3	Clip
Crystal Structure	fcc / bcc at 1673K		Clip
Lattice constant	508	fm	Clip
Melting Point	1973	K	Clip
Boiling Point	4773	K	Clip
Specific heat capacity	113	Jkg-1K-1	Clip
Thermal conductivity	54	Wm-1K-1	Clip

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See also: Periodic Table.